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base.js
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base.js
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import { EVENTS, NOTES, WIND_STRENGTHS, WORLDS } from '../constants'
import { WithParent } from '../mixins/with-parent'
/**
* The base class for shared logic of worlds.
* @extends WithParent
*/
class BaseWorld extends WithParent {
/**
* @param {PropertiesWithParent}
*/
constructor (properties) {
super(properties)
/**
* Holds the melody to be played while visiting this world.
* @type {Array<Number|undefined>}
*/
this.melody = []
/**
* Flag to indicate, whether this world is shown in the UI.
* @protected
*/
this._isActive = false
/**
* This is prepended to every document title change.
* @protected
*/
this._documentTitle = ''
/**
* This is appended to every document title change.
* @protected
*/
this._documentTitleRoot = 'Polygone - Trust Not Found - JS13kgames 2020'
/**
* Flag to track, whether music is already playing.
*/
this.__isPlayingMusic = false
/**
* How loud shall the music be played?
* @private
*/
this.__volume = 0.3;
this._updateView()
}
/**
* Add elements which are present in this world.
* To easier allow for separation in my mind, I tend to split it up in
* three chunks. SVG doesn't care however.
* @public
*/
addScene () {
this._addBackground()
this._addMiddleground()
this._addForeground()
}
/**
* Informs the game about a change in the wind.
* @public
* @fires {world:wind:change}
*/
fireWindChange () {
const dice = this._rollDice()
const { STILL, MEDIUM, STRONG } = WIND_STRENGTHS
const winds = [
null,
STILL, STILL,
MEDIUM, MEDIUM, MEDIUM,
STRONG,
]
const wind = winds[ dice ]
/**
* @event world:wind:change
* @type {{}}
* @property {{}} detail
* @property {string} detail.wind
*/
const event = new CustomEvent(EVENTS.WIND, { detail: { wind }})
this._eventNode.dispatchEvent(event)
}
/**
* Is this world currently shown?
* @public
* @returns {Boolean}
*/
isActive () {
return this._isActive
}
/**
* Inspired by Maxim (but can't used `with` blocks in strict mode)
* Taken from {@link https://xem.github.io/miniMusic/simple.html}
*
* Assume, each note is an eigth note (quaver). Apply multiplicator
* @see {@link http://www.sengpielaudio.com/calculator-bpmtempotime.htm|BPM calculus}
* @todo Check against a setting to control volume.
*/
playMusic () {
// See also https://www.artofcomposing.com/how-to-compose-music-101
// And https://twitter.com/mknol/status/1301193570842484738
// More tools at https://twitter.com/MaximeEuziere/status/1288918702776356866
if (this.melody.length > 0 && !this.__isPlayingMusic) {
const bpm = 120 * 2 /* since quaver instead of crotchet */
const minInS = 1 * 60
const bpmForQuaver = minInS / bpm
const baseFrequency = NOTES.C
const audioContext = new AudioContext()
const gainNode = audioContext.createGain()
const oscillator = audioContext.createOscillator()
this.__isPlayingMusic = true
let previousTime = 0.1
oscillator
.connect(gainNode)
.connect(audioContext.destination)
oscillator.start(previousTime)
gainNode.gain.setValueAtTime(this.__volume, previousTime)
this.melody
.map((note) => {
const value = note.slice(0, 1)
const hz = NOTES[ value ]
const lengthOfNote = parseFloat(note.slice(1))
const time = bpmForQuaver * lengthOfNote
return {
hz,
time
}
}).forEach((note, index) => {
const { hz, time } = note
oscillator.frequency.setValueAtTime(hz, previousTime)
previousTime += time
})
gainNode.gain.setValueAtTime(0, previousTime + 0.1)
oscillator.stop(previousTime + 0.1)
this.__isPlayingMusic = false
}
}
/**
* Show this world.
* @public
*/
setActive () {
this._isActive = true
this._updateView()
document.title = this._documentTitle
? [
this._documentTitle,
this._documentTitleRoot
].join(' | ')
: this._documentTitleRoot
this.playMusic()
}
/**
* Hide this world.
* @public
*/
setInactive () {
this._isActive = false
this._updateView()
}
/**
* @protected
*/
_addBackground () {
// To be implemented in sub-classes
}
/**
* @protected
*/
_addForeground () {
// To be implemented in sub-classes
}
/**
* @protected
*/
_addMiddleground () {
// To be implemented in sub-classes
}
/**
* Listen to some events.
* @protected
* @return {{}}
*/
_getEventMap () {
return {
[ EVENTS.TICK ]: this.__handleGameTimeUpdate.bind(this),
[ EVENTS.VOLUME ]: this.__handleGameVolumeChange.bind(this)
}
}
/**
* Add a new element to the DOM.
* @param {HTMLElement} parent
*/
_mount (parent) {
const classes = ['world', 'world--' + this.constructor.worldName]
this.element = this._svg('g', {}, classes)
parent.appendChild(this.element)
}
/**
* Meant to randomise certain elements of the world.
* @protected
* @param {Number} [min=1] - Lower boundary.
* @param {Number} [max=6] - Upper boundary.
* @returns {Number}
*/
_rollDice (min = 1, max = 6) {
return Math.floor(Math.random() * ((max - min) + min) + min)
}
/**
* Updates UI of this element.
*/
_updateView () {
super._updateView()
if (this.isActive()) {
this.element.classList.remove('hidden')
} else {
this.element.classList.add('hidden')
}
}
/**
* Perhaps update the wind strength.
* @private
* @param {{}} clock
* @param {Number} clock.day
* @param {Number} clock.hour
* @param {Number} clock.minute
*/
__handleGameTimeUpdate (clock) {
if (clock.minute === 0) {
this.fireWindChange()
}
}
/**
* Handle change in volume by the user.
* @private
* @param {{}} eventDetail
* @param {Number} eventDetail.volume
*/
__handleGameVolumeChange (eventDetail) {
this.__volume = eventDetail.volume
}
}
/**
* Used as identifier for transitions between worlds.
* @static
* @readonly
*/
BaseWorld.worldName = WORLDS.BASE
export { BaseWorld }